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      04-14-2013, 01:10 AM   #1
john16443
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N55 Engine-Exhaust Question

No, not looking for a replacement system or anything like that. Just wondering if anyone else has noticed that the right side exhaust tip collects lots more loose black soot than the left side. I believe the exhaust system is common and splits after the downpipe, so why would one side exhibit the soot issue and the other doesn't?

Also, is the soot an indication of incomplete combustion or something? I can't imagine having that amount of unburned carbon going through the exhaust system can be good for the cats.

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      04-14-2013, 01:21 AM   #2
michaelthepsycho
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This is not unique to the N55. All 335i exhausts have a flap on one side to quiet / heat up the cat faster. Look up golf tee or trunk disconnect.
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      04-14-2013, 11:00 AM   #3
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+1 Soot is normally. When you punch the gas, the ECU needs to richen up the engine to prevent detonation. During warmup it's richer as well.

I've seen that on all vehicles with chrome tips (since it shows).
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      04-14-2013, 12:10 PM   #4
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Normal on all N54 and N55. I did the golf tee mod and now both are completely black so at least it matches. Some year I will clean it off.
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      04-15-2013, 03:05 PM   #5
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After looking up the left pipe and seeing the closed baffle with the engine on, I can see why the soot on the right side only. Did the golf tee mod, will see tomorrow if I keep it or not. After I did it I thought the same thing as CombatNinga, all I'm going to do now is see soot on both sides! At least there's exhaust coming out of both tips now.
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      04-15-2013, 03:45 PM   #6
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You really ought to just keep it the way it came from factory. There's a reason there's an exhaust flap in there.
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      04-15-2013, 03:53 PM   #7
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So I did golf tee mod a year ago when first got car. A few days after that got an engine malfunction error and took it to BMW. Forgot to re-connect that wire and they identified that as the issue. They reconnected and gave me back car without error. I left it as is and never saw the error again. I know everyone around here says there are no issues with golf tee mod but since that happened I've just left it alone and not bothered changing how it works.
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      04-15-2013, 04:10 PM   #8
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Quote:
Originally Posted by rr006rbc View Post
You really ought to just keep it the way it came from factory. There's a reason there's an exhaust flap in there.
Not necessarily. It's simply noise control so that the car has broader customer appeal. All PEs (BMW, DINAN etc) are free flow and let the engine breathe better so much that they give a ~3-5 hp bump at 6000+ rpm.

As for your question OP, soot buildup could be due to a range of factors. My SA's for both my wife's MCS and my 335 agree that the increased ethanol content in fuel these days (esp. in TX) contributes to the buildup.

(on N54s) The exhaust system splits after the secondary cats on E90s and cross pipes on E92s, and the differential buildup is due to the presence of the vacuum-controlled flap on one of the mufflers. All in all, it's nothing that you should worry about too much though...

To get the soot off the muffler tips, a super fine grade steel wool pad will do the trick. Forget commercial cleaners.
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      04-15-2013, 06:45 PM   #9
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The flap is for noise control. Eliminates the drone when you are stopped at a light, or under light cruise on the highway. My Dinan S2 tune disables it, and you do notice the drone when the car is hot and idling at a light.
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